The United States Department of the Navy was established by an Act of Congress on April 30th, 1798, to provide administrative and technical support, and civilian leadership to the United States Navy and the United States Marine Corps (and when directed by the Congress or President, the United States Coast Guard). It is headed by the Secretary of the Navy, also known as the SECNAV in naval jargon. He is assisted by an Undersecretary of the Navy. The Department was a cabinet position, along with the War Department which contained the US Army until 1947 when the National Military Establishment was formed. The National Military Establishment was later renamed Department of Defense (DOD) in 1949. The Department of the Navy then became a component of the DOD.